With the increased interest in optical communications, it has been found desirable to form optical circuits in which light is transferred from one type of element to another, such as from a semiconductor injection laser as a source of the light to a light detector of some kind. The optical circuit may be entirely through a waveguide in a substrate or may be partially through the air. However, in such circuits it is frequently desirable to have the light pass between waveguides of different cross-sectional geometries. For example, it may be necessary to transfer the asymmetrical output of an injection laser to a stripe optical waveguide, and then transfer the light to a waveguide having equal lateral and transverse mode size to provide a symmetric output beam. In another application it may be desirable to couple light from a waveguide formed of many layers to one in which the light travels through fewer layers. Various methods have been tried to achieve these transfers of the light which have included designing specific geometries and choosing specific materials for the waveguides to achieve a phased match between the two waveguides being coupled. However, such systems are difficult to design since the choice of materials and geometries is severely limited and the length of the coupled region must be precisely controlled. Another technique has been to use a coupling region which is tapered in thickness. However, this is also difficult to make.